The application effect of calcium chloride in controlling sludge expansion

Due to changes in certain factors, the mass of activated sludge becomes lighter, expanded, and the settling performance deteriorates. The SVI value continues to increase, and normal mud-water separation cannot be carried out in the secondary sedimentation tank. The sludge level in the secondary sedimentation tank continues to rise, eventually leading to sewage treatment. Mud loss causes the MLSS concentration in the aeration tank to excessively decrease, thereby destroying the sludge in normal process operation. This phenomenon is called sludge expansion. Sludge bulking is a common abnormal phenomenon in activated sludge process systems.

The activated sludge process is now widely used in sewage treatment. This method has achieved good treatment results in treating various organic wastewaters such as urban sewage, papermaking, printing and dyeing wastewater, catering wastewater, and chemical wastewater. However, there is a common problem in activated sludge trea

Adding calcium chloride can quickly and effectively control sludge expansion, and the SVI of activated sludge can be quickly reduced. After adding calcium chloride, the SVI dropped from the initial 309.5mL/g to 67.1mL/g; without adding calcium chloride, only changing the operating mode can also reduce the SVI of activated sludge, but the reduction rate is slower. Adding calcium chloride has no significant effect on the COD removal rate. The COD removal rate with calcium chloride is only 2% lower than the COD removal rate without calcium chloride.

After stopping adding calcium chloride, the sludge settling performance can still remain stable. After stopping the dosing, it was run for another 18 cycles. The SVI of the activated sludge basically remained at around 72 mg/L, and expansion did not occur again. This alleviates the problem of sludge re-expanding in the short term after stopping dosing.

tment of sewage, that is, the sludge is prone to expansion during operation. Sludge bulking is mainly divided into filamentous bacterial sludge bulking and non-filamentous bacterial sludge bulking. There are many reasons for its formation. The harm of sludge expansion is very serious. Once it occurs, it is difficult to control and recovery takes a long time. If control measures are not taken in time, sludge loss may occur, fundamentally damaging the operation of the aeration tank and causing the entire treatment system to collapse.

Adding calcium chloride can inhibit the growth of filamentous bacteria and facilitate the formation of bacterial micelle, thus improving the settling performance of sludge. When calcium chloride is dissolved in water, it will decompose to produce chloride ions. Chloride ions have a sterilizing effect in water and can kill some filamentous bacteria and inhibit sludge expansion caused by filamentous bacteria. After stopping adding chlorine, chloride ions can stay in the water for a long time, and filamentous bacteria do not grow excessively in the short term. Microorganisms can still form dense and regular flocs, which also shows that adding calcium chloride can inhibit filamentous bacteria. The growth has a good effect on solving the problem of sludge expansion.

After adding calcium chloride, the dominant bacterial flora in the activated sludge changed, the growth of filamentous bacteria was inhibited, and the number of bacteria was significantly reduced; regular, dense, and rounded edges were formed, and the flocs were relatively large and active. Improved sludge settling performance.